1. Field of the Invention
The present invention relates to the manufacture of semiconductor devices and, more particularly, to the selective removal of layers for integrated device manufacture and the manufacture of MEMS using an etching gas while preserving one or more underlying dielectric layers.
2. Description of Related Art
Vapor etching of semiconductor materials and/or substrates can be accomplished using gases such as XeF2, KrF2, or BrF3. In XeF2 etching, XeF2 gas reacts with one or more solid materials, such as silicon and molybdenum, such that the material(s) is/are converted to a gas phase. This removal of material by such etching is disclosed in, among other places, U.S. Pat. No. 7,638,435, which is incorporated herein by reference.
The selective removal of Si, SiGe, Ge, or transitional metals such as Ta, Ti and W, while preserving an underlying dielectric layer, such as silicon dioxide, silicon nitride or silicon carbide, is important in the manufacture of semiconductor devices and MEMS devices. This is also true for the removal of nitrides and alloys of transitional metals.
XeF2 gas is often used for such removal since it etches many of the foregoing materials and the rate at which the etched material(s) is/are removed is much higher than the rate for one or more underlying dielectric materials. However with certain pairs of materials—for example silicon as the etched material and silicon nitride or silicon carbide as the dielectric—the chemical reaction between the XeF2 and the etched material undesirably increases the etching of the dielectric material thereby reducing or eliminating the advantages of selective etching
What is, therefore, needed is a method for vapor etching semiconductor or MEMS devices/substrates that enables the effective removal of one or more top layers of materials while substantially preserving (i.e., not removing too much of) one or more underlying dielectric material(s).